guests = ['张卓诚','肖子杰','张启恒','黎可']
#for i in guests:
    #print('尊敬的{}先生，感谢你刚刚的捐赠！！！'.format(i))
list1 = ['a','b','d','c']
for x in list1:
    if ( x !='a') + ('c'==x) + ('d'==x) + ('d'!=x) == 3:
        print(x)
        break
    
